The overall UW ACE proposal is centered on a comprehensive developmental model of risk, risk processes, symptom emergence, and adaptation in autism spectrum disorder (ASD). According to this model, early autism risk factors (genetic/familial and environmental) lead to risk processes, namely altered patterns of interaction between the child and his/her environment, which contribute to the abnormal development of neural circuitry and atypical behaviors. Project III has two broad goals: in a study of infant siblings of children with autism, we will (1) determine the predictive validity of measures of early prelinguistic abilities as risk indices for language impairment and ASD, and (2) examine the influence of early intervention on the development of speech perception, speech preferences, and acquisition of speech in infants at risk for ASD. Our studies of early speech perception have demonstrated predictive relationships between the proposed measures of basic language perception/production and later measures of language and vocabulary in typically developing (TD) infants. In addition, our studies of preschool age children found critical differences in measures of phonetic discrimination and social communication between children with ASD and children with typical development and developmental delay. Based on converging lines of research with TD children and children with ASD, the proposed measures of speech production and linguistic and social responsiveness to speech are hypothesized to be extremely sensitive to the degree of risk for autism. This project directly addresses goals outlined in the NIH Autism Research Matrix: (1) Identification of the biological and/or behavioral risk indices in infancy for the development of autism and autism-related symptoms, such as language and social impairments; (2) identification of individual characteristics that predict response to behavioral treatment; and (3) provision of evidence that cases of autism might be secondarily prevented through early identification and early treatment. It will also impact theories of speech and language development, and general theories of developmental neuroscience. The methods available to this laboratory, and the set of questions posed to examine infant speech development, form a broad and very powerful set of tools to advance our knowledge in these fields.